Temporally-Delineated Sources of Major Chemical Species in High Arctic Snow

Abstract

Abstract. Long-range transport of aerosol from lower latitudes to the high Arctic may be a significant contributor to climate forcing in the Arctic. To identify the sources of key contaminants entering the Canadian high Arctic an intensive campaign of snow sampling was completed at Alert, Nunavut, from September 2014 to June 2015. Fresh snow samples collected every few days were analysed for black carbon, major ions, and metals, and this rich data provided an opportunity for a temporally-15 refined source apportionment of snow composition via Positive Matrix Factorization in conjunction with FLEXPART potential emission sensitivity analysis. Seven source factors were identified: sea salt, regional dust, Eurasian fossil fuel combustion, mixed carboxylic acid sources, nitrate processing, Eurasian industrial activities, and regional volcanic and marine biogenic activity. The majority (73%) of the black carbon in snow, a light-absorbing compound critical to the Arctic radiative balance, was found to be the product of fossil fuel burning with limited biomass burning influence. 20

Processes Controlling the Composition and Abundance of Arctic Aerosol

“…Source apportionment of deposited black carbon and other light absorbing aerosol components in surface snow is sparse and has yielded varying results. Some work indicates a dominance of biomass burning sources in both Eurasia and North America (Hegg et al, , ), while other work indicates the importance of anthropogenic fossil fuel sources in Eurasia (Macdonald et al, ; Q. Wang et al, ) and is more consistent with attribution of lower tropospheric aerosol (section ). The relative importance of sources likely also varies with the location of the observations.…”

“…The extent of aerosol removal, both within Arctic regions and during transport, is an important determinant of Arctic aerosol abundance and can have a significant impact on snow and ice albedo. Observations of snow composition across the Arctic illustrate the presence of black carbon and other light absorbing aerosol (including brown carbon and mineral dust) in surface snow (e.g., Clarke & Noone, ; Doherty et al, ; Hegg et al, ; Macdonald et al, ; Q. Wang et al, ). Source apportionment of deposited black carbon and other light absorbing aerosol components in surface snow is sparse and has yielded varying results.…”

“…Such estimates indicate deposition velocities in rough agreement with those from direct eddy‐covariance measurements; with values up to ∼0.6 cm/s and some variability depending on the chemical species measured (e.g., Bergin et al, ; Davidson et al, ; Dovland & Eliassen, ; Hillamo et al, ; McMahon & Denison,). At Alert, some of the first full year measurements of both snow chemistry and ambient aerosol has provided measurements of the deposition velocity for many aerosol species (Figure ; Macdonald et al, , ). Black carbon, ammonium, and sulfate deposition velocities were in the range expected for dry deposition during winter, while estimated deposition velocities increased in spring and fall demonstrating the shift to wet removal (section ; Macdonald et al, ).…”

Observed and Modeled Black Carbon Deposition and Sources in the Western Russian Arctic 1800–2014

“… 5 , 6 However, some European Arctic ice core and lake sediment data show increasing BC deposition trends since the 1970s 7 , 8 and suggest spatially variable BC trends. 9 Observational data providing constraints on BC sources for the Arctic are mainly available for atmospheric, 10 , 11 snow, 12 , 13 and estuarine surface sediments, 14 which represent snapshots in time. While BC sources and particularly their trends are poorly constrained in most of the Arctic, atmospheric isotopic BC source analyses suggest that the spatial allocation of emissions and their source contributions in emission inventory-based models may need significant improvement.…”